RAW format: what is it. RAW or JPEG which is better?

RAW is translated from English as "raw, incomplete." If in ordinary life this quality cannot be considered a plus, then in digital photography the “raw” format is the most advanced. Only the most serious digital cameras allow you to save pictures in RAW, to postpone some of the important settings to the processing stage and squeeze the most out of photographic equipment.

What is RAW

If universal JPEG and TIFF image formats can be considered the digital equivalent of a slide (or final print), then RAW is an analogue of film negative. "Semi-finished product", involving various options for further processing, during which this or that result will be obtained.

To understand the meaning of the "raw" format, it is worth going from the opposite. When using JPEG, the picture goes through five stages: capturing an analog signal by a matrix, digitizing (analog-to-digital converter), color interpolation, processing in accordance with the camera settings, compression with loss of quality. Half of the settings are found in any cameras, including film ones (exposure, ISO sensitivity, metering method, autofocus operation). The remaining settings are related to the JPEG format: * Color rendering. Various options ("lively", "saturated", "natural colors"). Monochrome shooting modes. Correction of RGB color components. * White balance. If the picture is blue or red, the wrong White Ballance setting is selected. * Brightness and saturation. * Microcontrast. Appears under the English word sharpening or Russian "sharpness", although this is not related to real sharpness. * Compression ratio. Different options like “super-fine” in reality only mean that losses are minimized.

Converted RAW file. © www.birdinfo.co.za

JPEG image. © www.birdinfo.co.za

The digital “negative” is written to the card immediately after the digitization phase of the analog signal. Its use allows you to postpone all these settings to the processing stage on the PC.

Color interpolation

A typical digital camera matrix consists of cells located on the same plane, which respond only to brightness, forming a monochrome image. To get information about color, Kodak engineer Bruce Bayer 20 years ago proposed installing a filter in front of each cell in one of three colors - green, red and blue, which in total give the desired shade. This technology is used to this day. For each cell with red and blue filters, there are two with green, since this color contains basic information about brightness. After being converted to digital form, the picture consists of pixels of red, green and blue. For immediate operation, such an intermediate image is unsuitable. In order for each pixel at the output to have a natural hue (that is, to include all three color components), the camera processor or RAW converter sums the color of neighboring pixels, for which a complex color interpolation algorithm is used.

Automatically import RAW files into Adobe Lightroom.

Depending on the manufacturer and the specific DPC model, the RAW file may contain data both before interpolation and after (until the final processing stage). Most modern digital cameras use the first approach, since RAW conversion programs almost always offer better algorithms. In addition, they are constantly being improved, and the processor of the camera can be changed by buying a new one. Improving in-camera JPEG algorithms is developing in parallel with improving matrices. It often determines the advantages of new models over their predecessors - for example, the Nikon D40 DSLR over the D70. The same matrix, but the D40 is a more recent model, and therefore it provides better JPEG quality. But even better quality can be achieved by shooting on the D70, if at all to abandon the JPEG format!

Raw quality

There is always potentially more information in a RAW file than in the final. RAW converters use this data in various ways. Some are better suited for processing underexposed images, while others “squeeze” the maximum out of those taken with optimal settings. Typically, an ADC (analog-to-digital converter) provides a color depth of 12 bits. There are more advanced exceptions: Canon 40D (14 bit), Fuji S5 Pro (14 bit x 2), Pentax K10D (22 bit). When shooting in JPEG format, we get the usual 8-bit files, immediately suitable for printing. "Extra" information is used by the processor to compensate for the shortcomings of the matrix number (a narrow range of brightness, noise). But even in the most powerful and advanced models, “extra” information is not used 100%. RAW stores all the information that the ADC unit provides, including the original bit depth (color depth). After the files are copied to the computer, you decide what to do with 12-bit data. 12-bit RAW enables safe exposure compensation within two exposure levels in each direction. Using the exposure compensation tool in the RAW converter (just moving the slider), you shift the working area of ??the final file (8-bit). If your camera is slightly mistaken in the choice of exposure parameters, this will allow you to “stretch” the shadows and lights without any tonal distortions or other side effects that occur in the case of a serious tone correction. If the exposure is initially precisely defined, due to the greater bit depth, you can get deeper, more detailed images by converting raw files to TIFF format with 16-bit color. Bit depth RAW allows you to use this format for taking photos with an extended dynamic range - High Dynamic Range (HDR).

Variety of formats

If the RAW format were the same for all manufacturers, it would be very convenient in terms of software compatibility. There have been attempts in history to create a universal standard for digital negativity similar to JPEG and TIFF. The most successful of them is the Digital Negative (DNG) format from Adobe, which has found application in some modern DSCs (Leica M8, Pentax K10D, Samsung GX-10). However, this is an exception to the general rule. Not only does each manufacturer promote its own standard of “raw” files (CR2, NEF, PEF, variations with the RAW extension), the formats do not match within the same manufacturer’s line: as a rule, software updates are required for each new generation of DSCs. Formats differ not only in terms of data structure. Sometimes manufacturers save space on memory cards using raw data compression (for example, as in the case of Nikon Electronic Format). Theoretically, such compression can lead to a slight loss of quality. In practice, even minimal losses are absent. The only drawback is that the compression process itself consumes resources and can affect the recording speed of images. The raw Pentax (PEF) format embodies the opposite approach.

When not to shoot in RAW

RAW-format provides the best quality and the ability to make even the most unsuccessful shots something pleasing to the eye. But there are several situations when shooting in RAW is not practical: insufficient memory card, burst shooting (on some “slow” cameras), domestic shooting, direct printing, lack of personal time for image processing.

Leila Allam

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